From the Post Scores Page
Access the Tournament.
Click Post Scores.
Select a division.
Under the division dropdown, select Post Scores.
Locate the game and uncheck the Final box.
Change the filter to Show All Games or Show Final Games, if necessary.
Edit the scores as needed, and re-check the Final box.
From QuickScore
Log in and navigate to the Tournaments page.
In the top-right, click QuickScore.
Select a tournament.
Click Post Scores by Division or Post Scores by Complex.
Select a division or a facility.
Locate the game, click the dropdown arrow, and uncheck the Mark as Final box.
Change the filter to Show All Games or Show Final Games, if necessary.
Edit the score as needed and re-check the Mark as Final box.